We found this circuit in a 1964 Electronic Design. It provides 0.5 V signals from 4 kHz subcarriers. Transistors are from the era.
This circuit is suitable for SSB modulation and was obtained from an amateur radio documentation from...
This circuit was obtained in a 90’s Popular Electronics. The operators admit equivalents such as...
This 7400 TTL circuit has a memory, keeping the LED on when a pulse is detected. The circuit must be...